Ventilation system for a papermaking machine



May 27, 1969 VENTILATION Filed April 27. 1967 INVENTOR. RAYMOND C. CLARK ATTORNEY y 7, 1969 R. c. CLARK 3,445,938

VENTILATION SYSTEM FOR A PAPERMAKING MACHINE INVENTOR.

RAYMON D C. CLARK ATTORN EY y 7, 1969 R. CLARK 7 3,445,938

VENTILATION SYSTEM FOR A PAPERMAKING MACHINE Filed April 27. 1967 Sheet 3 of s INVENTOR RAYMOND C. CLARK United States Patent 3,445,938 VENTILATION SYSTEM FOR A PAPERMAKING MACHINE Raymond C. Clark, Orange, Conn., assignor to Huyck Corporation, Stamford, Conn., a corporation of New York Filed Apr. 27, 1967, Ser. No. 634,337 Int. Cl. F26h 13/08 US. Cl. 34-116 12 Claims ABSTRACT OF THE DISCLOSURE The present invention is directed to an improved apparatus for removing or purging the moist air from the tentlike pockets of the dryer section of a papermaking machine. More specifically, the present invention provides improved means for supplying fresh air into these tentlike pockets, the result being to force the moist air therein to the lateral edges of the machine where such air may be removed from the machine.

Background of the invention In the typical papermaking machine such as the socalled Fourdrinier machine, an aqueous suspension of fibers, called the furnish is flowed onto a travelling forming medium, generally an endless woven belt of Wire and/or synthetic material, to form paper or paper-like material, such as board, pulp, asbestos sheet, or the like. As the forming medium travels through the forming section of the machine, much of the Water is removed from the furnish and a somewhat self-supporting continuous paper web is formed. This Water removal is facilitated by the use of such well-known devices as hydrofoils, table rolls and/ or suction boxes.

The somewhat self-supporting paper web is then transferred to the press section of the machine, where still more of its water content is removed. This is accomplished by passing the paper web through a series of nips formed by cooperating press rolls; these press rolls also serving to compact the web.

Finally, the paper web is transferred to the dryer section of the machine where it is passed about and held in contact with a series of heated, generally cylindrical dryer rolls to remove still further amounts of water therefrom. In most instances, the dryer rolls will be arranged in upper and lower parallel arrays with the continuous web being passed upward and downward in a serpentined manner about the rolls. The surface of the dryer rolls usually is imperforate and the web is held in contact therewith over at least a portion of the surface thereof by an endless, and preferably porous backing material (commonly referred to as a dryer fabric). Recent advances in the papermaking art have shown that in some instances, the dryer roll surface may be made gas-pervious, so that steam or other suitable drying media may pass therethrough to increase the amount of water removed from the paper web.

In the past, dryer fabrics have generally been made of a relatively impervious, blanket-like construction. However, the modern trend is to utilize an open weave porous material, usually of natural synthetic fibers, as such open Weave fabrics readily permit fluids to pass therethrough. In some instances, perforated plastic belts and the like have also been found suitable for such uses.

In the dryer section of the machine, there is a tendency for steam and/ or moisture laden air, generated as a result of the vaporization of water from the web, to become trapped within pockets formed in the machine. There are those pockets formed by each dryer fabric alone; these being located above the upper and below the lower arrays of dryer rolls respectively and there are those tent-like ice pockets which are located between the upper and lower arrays of dryer rolls. Those pockets formed by the dryer fabrics alone comprise the area enclosed by the dryer fabrics as they travel their separate endless paths. Those tent-like pockets located between the upper and lower arrays of dryer rolls are those areas enclosed (in the order named) by a dryer roll surface in one array, the paper web, the dryer fabric in the other array, and the paper web. In the former instance there generally will be only two pockets whereas in the latter instance, there may be many individual tent-like pockets. As the build-up of moist air in these pockets hinders further removal of water from the web, and as this build-up also may create a non-uniform moisture profile across the web, it is generally desirable to provide means for removing or purging the moist air from the pockets.

In many instances, large blowers or exhaust fans have been used to move fresh air laterally through the dryer pockets in order to remove the moist air. However, these methods require a somewhat large capital expense and may also result in a non-uniform purging of the pocket; the latter creating a non-uniform moisture profile across the web. Further, should the air blown into the pockets be under too great a pressure, sheet flutter may occur, the result being wrinkling or possibly breakage of the paper web.

Other methods of introducing fresh air into the dryer pockets under pressure have been attempted, such as blowing air through or around the pocket guide rolls and through the fabric into the pocket. However, these methods often prove unsatisfactory, as technical problems may arise in providing suitable sealing means and/ or preventing sheet flutter.

Therefore, one object of the present invention is to provide an improved apparatus for purging moist air from the tent-like pockets in the dryer section of the papermaking machine.

Another object of the present invention is to provide means for purging moist air from the dryer pockets in the papermaking machine without causing flutter in the web of paper-like material.

Another object of the present invention is to provide an improved means for uniformly purging a dryer pocket in a papermaking machine.

Still another object of the present invention is to provide a means for removing moist air from the dryer section of a papermaking machine which does not require the addition of auxiliary devices to the machine.

A further object of the present invention is to provide a means for removing the moist air which tends to collect in pockets in the dryer section of a papermaking machine, the means requiring relatively simple modification of existing machines.

Summary of the invention In accordance with the principles of the present invention, one embodiment thereof comprises a papermaking machine including first and second arrays of heated generally cylindrical dryer rolls for drying a continuous web of paper or paper-like material which is passed about and held in contact with at least a portion of the surface of each of the rolls. A porous backing fabric is associated with each array of dryer rolls and is arranged to maintain the continuous web in intimate contact with the surface of the rolls. Fabric guide rolls are associated with the porous backing fabrics and provide means for guiding the fabrics about their separate endless paths; the fabrics contacting at least a portion of the surface of the guide rolls. Included in such guide rolls are pocket rolls which are those guide rolls disposed between adjacent dryer rolls in each array; the backing fabrics passing over a portion of the surface thereof as they travel between adjacent dryer rolls.

The guide rolls, including the pocket guide rolls, are generally cylindrical in shape and extend longitudinally across the width of the backing fabric. Generally, the guide rolls engage the side of the backing fabric opposite the side of the fabric which engages the web. At least one of the guide rolls has at least one annular or helical groove in the peripheral surface thereof. Rota tion of the roll, together with the movement of the porous backing fabric combine to produce a flow of fresh air through the dryer fabric to purge moist air therefrom.

Thus, it can be seen that since the pocket rolls extend completely across the width of the dryer fabric, a uniform flow of fresh air enters or leaves the dryer pockets to purge the moist air therefrom.

Additional objects and advantages of the present invention together with a better understanding thereof may be had by referring to the following detailed description of the present invention together with the accompanying v drawings.

Brief description of the drawings FIGURE 1 is a diagrammatic view of the dryer section of a papermaking machine;

FIGURE 2 is an enlarged view of a portion of the dryer section shown in FIGURE 1;

FIGURE 3 is a View of a pocket guide roll with a partial section taken along lines A-A' in FIGURE 2, the pocket guide roll being constructed in accordance with the principles of the present invention; and

FIGURE 4 is a similar view of an alternate embodiment of the pocket guide roll shown in FIGURE 3.

FIGURE 5 is a similar view of another embodiment of the pocket guide roll shown in FIGURE 3.

FIGURE 6 is a diagrammatic illustration of a fabric useful in the practice of the present invention.

Description of the preferred embodiments Referring now to the drawings, and in particular to FIGURE 1, there is shown a first or upper array of dryer cans 10, 12 and 14 and a second or lower array of dryer cans 18, and 22. The dryer cans are preferably smooth, imperforate metal cylinders arranged for rotation upon suitable bearings (not shown) and generally supplied with steam which is introduced to the interior of each of the dryer cans at appropriate temperatures. In some instances, the surface of one or more of the dryer cans may be of a porous nature through which heated air or steam flows to increase the drying of the paper web. Preferably, the upper and lower arrays of the dryer cans are arranged in parallel rows with the dryer cans in the upper array being staggered with respect to the respective dryer cans in the lower array. There is also shown adjacent to the last dryer can 14, a cylinder 28 which may be a baby dryer or a guide roll about which the web to be dried passes as it travels to be further processed or collected.

A web to be dried (for illustrative purposes the web is assumed to be a web of paper or paper-like material) is travelling from left to right as shown in the figure. The web 30 is guided downwardly about the lower dryer can 18, upwardly around the upper dryer can 10 and sequentially around the remaining lower and upper dryer cans in a serpentined manner. When the web 30 leaves the last illustrated dryer can 14, it may be guided by the roll 28 to additional sections of the machine or to a reel for collection.

A first or upper fluid permeable or porous backing (dryer) fabric 32 is associated with the upper array of dryer cans 10, 12 and 14 and is arranged so as to maintain the web in intimate contact with at least a portion of the periphery of each of the dryer cans in order to liberate moisture therefrom. The dryer fabric 32 must be of such a nature as to readily permit fluids to pass therethrough and is generally an endless (seamed or joined) belt conducted through a closed path; the path being defined by the dryer cans 10, 12 and 14 by a combination of guide rolls or other similar devices which extend across the width of the fabric and which guide the fabric on this path. Such guide rolls may include felt rolls 34, return rolls 36, tensioning rolls 38 and pocket rolls 40 and 42 (the pocket rolls being those felt or fabric guide rolls disposed between adjacent dryer cans 10, 12 and 14 respectively). Preferably, the center line of the pocket rolls 40 and 42 are positioned below the center line of the dryer cans in the upper array with the pocket rolls being positioned between adjacent successive dryer cans in such a manner that the dryer fabric is caused to traverse a portion of the surface of each of these dryer cans in order to hold the web in intimate heat transfer relationship with each of the dryer cans.

As will be discussed in greater detail hereinafter, it is preferred that the dryer fabric 32 be of a nature as the dryer fabric disclosed and claimed in Clark, United States Patent No. 3,325,909, assigned to the same assignee as the present invention. While not wanting to be limited to the specific construction of the dryer fabric set forth therein, it is noted that the dryer fabric set forth therein is of such a construction that as the fabric travels free of contact on either side thereof, the construction of the fabric causes air to be forced or pumped from one side of the porous fabric to the other side thereof through the openings therein. This air movement is depicted in FIGURE 2 by the air-flow arrows about pocket roll 40, for example. Generally, this may be obtained by orienting the Weave of the fabric, if the fabric is a woven structure, at an angle with respect to the path of travel thereof. As set forth in United States Patent No. 3,325,909, at column 2, lines 65-70, fabrics which will meet the requirements of the present invention may be woven in particular patterns of interlacing of warp and filling yarns whereby the transversely extending yarns will fall into pairs or groups which make up the equivalent of sloping slots with sloping passageways therebetween. For example, in one embodiment of United States Patent No. 3,325,909, and as depicted in FIGURE 6 of the present application, the transversely extending slots are each made up of a plurality of parallel yarns, cords or the like 102 laid up in a staggered stack and secured together, as by an adhesive or settable impregnant to form elongated structures having cross-sections in the shape of parallelograms with inclined sides to establish the desired degree of slant to be assumed in the finished fabric. These slots 100 are interwoven with warp yarns or cords 104 and 106 which cross between each slot much in the manner of a leno-wave fabric (see column 9, lines 51-60). It is also believed that a similar result can be obtained with a perforated plastic belt or the like, by orienting the openings in the belt at an angle with respect to the plane of the belt. However, it is not the intention of the present invention to be limited to such fabric constructions, as such is given by way of example only. Other suitable porous or fluid permeable dryer fabrics include DRI-FAB fabrics, all synthetic, open weave dryer fabrics manufactured and sold in the United States by the Formex Company Division of I-Iuyck Corporation and perforated plastic belts.

Similarly, a second or lower porous dryer fabric is associated with the lower array of dryer cans 18, 20 and 22, the second or lower dryer fabric 48 also comprising an endless belt which may be identical with the first dryer fabric 32 and which is similarly conducted through an endless path defined by the dryer cans 18, 20 and 22 and suitable guide rolls. In this instance, the guide rolls comprise felt rolls 50, return rolls 52, tensioning rolls 54, and pocket felt rolls 56 and 58, the pocket felt rolls 56 and 58 being those felt rolls disposed between adjacent dryer cans 18, 20 and 22 respectively. As the lower dryer fabric 48 may be constructed in a manner identical to the upper dryer fabric 32, it too may cause air to be pumped therethrough as it travels free from contact on either surface.

The tent-like pockets which lie between the upper and lower arrays of dryer cans are difficult to ventilate. Specifically, these tent-like pockets are formed between the 'upper 32 and lower 48 dryer fabrics and, as previously mentioned, are separated by the paper web 30 as it serpentines its way through the dryer section of the machine. In order to facilitate the discussion of the present invention, the tent-like pockets shown in FIGURE 1 are numbered from left to right 62, 64, 66 and 68 respectively.

Also difiicult to ventilate are the areas or pockets enclosed by the dryer fabrics as they travel their endless path; these areas being numbered 69 and 71 in FIGURE 1.

In accordance with the principles of the present invention, and referring now to FIGURE 3, 4 and 5, at least one of the guide rolls is constructed so as to have at least one groove in the peripheral surface thereof. The groove or grooves may be annular 75 or radial and axially spaced, as shown in FIGURE 3 or they may be helical 77 as shown in FIGURES 4 and 5. It is preferred that the guide rolls be of a solid construction with the grooves being machined or otherwise cut through the surface thereof. While not wanting to be bound by a theory of operation, it is believed that the improved air movement into, or out of as the case may be, the pockets occur as the result of the centrifugal forces on the air which becomes entrained within the grooves on the grooved guide roll or rolls. That is, for example, air entrained in the grooves of a pocket roll will be forced tothe outer portions of the grooves where it will be forced through the fabric into the tent-like dryer pockets. By providing such grooved pocket rolls, a greater amount of fresh air will be pumped through the dryer fabric into the tent-like pockets than will be provided by a solid roll.

When the pocket roll has axially spaced, annular or radial grooves in the peripheral surface thereof, it may be desired to provide additional means for exhausting the moist air and/ or steam from the tent-like pockets, which means might include a hood or other suitable means for -moving the air laterally through the pockets. However,

it may be desired to permit the moist air to build up within the tent-like pockets and set up a natural current which will force the air laterally out of the pockets. When helical grooves such as those shown in FIGURE 4 are used, rotation of the roll may influence the flow of air and tend to set up a flow of air across the fabric. This natural tendency of the air to move from one side of the machine to the other in many instances will eliminate the need for additional exhaust means for the machine.

In most instances, the pocket felt rolls will be constructed of a stainless steel material; however, it is not the intention of the present invention to be limited thereto as such is given by way of example only.

It can be seen that the felt guide rolls 34, 50 and/or the return guide rolls 36 and 52 may also be made of a grooved construction, to cause a flow of air to be set up to move moist air out of the pockets 69 and 71. That is, the grooved rolls will force the moist air in the pockets 69 and 71 to move to the outside thereof in order to reduce the amount of moist air therein.

Example In a paper machine clothed with a standard, all synthetic open weave dryer fabric travelling at a machine speed of 2,000 feet per minute and utilizing smooth (no grooves) pocket rolls, it was measured that 140 cubic feet of air per minute per lineal foot of machine width were pumped through the dryer fabric into one of the tent-like pockets on the opposite side of the fabric from one of the pocket rolls. However, when the smooth pocket roll was replaced by a pocket roll having a plurality of annular, axially spaced grooves in the surface thereof, and the dryer fabric was operating at the same 6 machine speed of 2,000 feet per minute, 220 cubic feet of air per minute per lineal foot of machine width were pumped through the same dryer fabric, an increase of some 57%.

It can readily be seen that means for purging dryer pockets such as shown and described hereinbefore will provide an economical method of enhancing the removal of moist air and still provide a uniform moisture profile in the web. Further, such a system requires only slight modifications of the existing papermaking machinery and will not entail expensive or elaborate modifications of existing machinery or designing of new machines.

While I have shown and described a particular embodiment of the present invention, it will be obvious to those skilled in the art that various changes and modifications may be made to the present invention without departing therefrom in its broader aspects.

What I claim as new and novel and desire to secure by Letters Patent of the United States is:

1. A papermaking machine including,

(A) An array of heated, generally cylindrical rolls for drying a continuous web of material passing about at least a portion of the surface thereof;

(B) An endless, fluid permeable backing fabric associated with said array of dryer rolls and arranged to maintain the web in intimate contact with at least a portion of the surface of each of said dryer rolls; and

(C) Guide rolls about a portion of whose surface said backing fabric passes as said fabric travels along its endless path, said guide rolls extending longitudinally across the width of said backing fabric, at least one of said guide rolls having at least one helical groove in the peripheral surface thereof for pumping air through said fabric.

2. A papermaking machine of the character described in claim 1 wherein said guide roll has at least two axially spaced, helical grooves in the peripheral surface thereof.

3. A papermaking machine of the character described in claim 1 wherein at least one of said guide rolls having a grooved surface is a pocket guide roll disposed between adjacent dryer rolls.

4. A papermaking machine of the type described in claim 1 wherein all of the guide rolls disposed between adjacent dryer rolls have at least one groove in the peripheral surface theerof.

5. A paperrnaking machine including,

(A) An array of heated, generally cylindrical rolls for drying a continuous web of material passing about at least a portion of the surface thereof;

(B) An endless, fluid permeable backing fabric associated with said array of dryer rolls and arranged to maintain the web in intimate contact with at least a portion of the surface of each of said dryer rolls, said fabric having pore openings oriented such that when said fabric travels free of contact on either side, air is pumped through the pore openings therein from one side to the other side thereof; and

(C) Guide rolls about a portion of whose surface said backing fabric passes as said fabric travels along its endless path, said guide rolls extending longitudinally across the width of said backing fabric, at least one of said guide rolls having at least one groove in the peripheral surface thereof for pumping air through said fabric.

6. A papermaking machine of the character described in claim 5 including a pocket guide roll disposed between adjacent of said dryer rolls, each of said pocket guide rolls having at least a single groove in the peripheral surface thereof.

7. In the dryer section of a papermaking machine having an array of heated generally cylindrical dryer rolls for drying a continuous web being passed about and held in intimate contact with at least a portion of the surface of said rolls by an associated porous backing fabric, and having pocket guide rolls disposed between adjacent of the dryer rolls for maintaining tension of the porous backing fabric as the porous backing fabric passes between adjacent dryer rolls, the pocket guide rolls extending longitudinally across the width of said porous backing fabric and the porous backing fabric passing about at least a portion of the surface of each of the pocket guide rolls; the improvement wherein at least one of said guide rolls includes at least one continuous helical groove in the peripheral surface of at least a portion thereof.

8. A papermaking machine including,

(A) A first array of heated, generally cylindrical rolls for drying a continuous web of material passing about at least a portion of the surface thereof;

(B) A secondary array of heated, generally cylindrical rolls for drying a continuous web of material passing about at least a portion of the surface thereof, said second array spaced from and generally parallel with said first array;

(C) An endless, porous backing fabric associated with each of said arrays of dryer rolls and arranged to press and maintain the web in intimate heat transferring contact with at least a portion of the surface of each of said dryer rolls, said fabric having pore openings oriented such that when said fabric travels free of contact on either side, air is pumped through the pore openings therein from one side to the other side thereof whereby the amount of air pumped through said fabric in the area of said grooved guide rolls is increased; and

(D) Guide rolls associated with each of said backing fabrics about a portion of whose surface said fabrics pass as said fabrics travel about their respective endless paths, said guide rolls extending substantially across the width of said backing fabrics;

Said guide rolls including pocket guide rolls disposed between adjacent dryer rolls in each of said arrays, at least one of said pocket guide rolls having at least a single groove in the peripheral surface thereof.

9. A papermaking machine as described in claim 8 wherein each of said pocket guide rolls includes at least one groove in the peripheral surface thereof.

10. A papermaking machine as described in claim 8 wherein at least one of said pocket guide rolls includes a helical groove in the peripheral surface thereof.

11. In the dryer section of a papermaking machine having an array of heated, generally cylindrical rolls for drying a continous web of paper or paper-like material passed about and held in intimate contact with at least a portion of the surface thereof by an associated endless porous backing fabric and having guide rolls about a portion of Whose surface the porous backing fabric passes as it travels about its endless path, the guide rolls extending longitudinally across the width of said porous backing fabric, the improvement comprising at least one of said guide rolls including at least one helical groove in the peripheral surface thereof for pumping air through the fabric in the area of said guide roll.

12. A papermaking machine of the type described in claim 11 wherein said guide roll includes a plurality of axially spaced, helical grooves in the peripheral surface of said roll.

References Cited UNITED STATES PATENTS 3,320,677 5/1967 Reitzel 34ll6 XR CARLTON R. CROYLE, Primary Examiner.

ALLAN D. HERRMANN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,445,938 Dated May 27, 1969 Inventor(s) Raymond C. Clark It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 17, "FIGURE" should read FIGURES Column 6, line 18, after "aspects." insert Therefore, it is the intention of the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the present invention. Claim 4, "theerof" should read thereof Claim 8, (B) "secondary" should read second Signed and sealed this 20th day of March 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PC1-1050 (10-69) USCOMM-DC 60376-5 69 Q U S. GOVEIRMEN" FIINHNG OFFICE lll 0-368-334, 

